The Vudu-X replaces your carbon rod dampener with a patented, highly advanced compound bow string silencer. The Vudu-X traps the string in a recoil chamber, eliminating resonant strikes while also absorbing limb shock. Both carbon rod versions (8") can be shortened for a perfect it. To determine if you need a 5/16” or 3/8” rod take a 5/16” open-end wrench and slip it over the stock rod. If it does not fit then you have a 3/8” rod.